STM32L081CB datasheet(25/110 Pages) STMICROELECTRONICS

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STM32L081xx

Functional overview

3.10

Direct memory access (DMA)

The flexible 7-channel, general-purpose DMA is able to manage memory-to-memory,

peripheral-to-memory and memory-to-peripheral transfers. The DMA controller supports

circular buffer management, avoiding the generation of interrupts when the controller

reaches the end of the buffer.

Each channel is connected to dedicated hardware DMA requests, with software trigger

support for each channel. Configuration is done by software and transfer sizes between

source and destination are independent.

The DMA can be used with the main peripherals: AES, SPI, I2C, USART, LPUART,

general-purpose timers, and ADC.

3.11

Analog-to-digital converter (ADC)

A native 12-bit, extended to 16-bit through hardware oversampling, analog-to-digital

converter is embedded into STM32L081xx device. It has up to 16 external channels and 3

internal channels (temperature sensor, voltage reference). Three channels, PA0, PA4 and

PA5, are fast channels, while the others are standard channels.

The ADC performs conversions in single-shot or scan mode. In scan mode, automatic

conversion is performed on a selected group of analog inputs.

The ADC frequency is independent from the CPU frequency, allowing maximum sampling

rate of 1.14 MSPS even with a low CPU speed. The ADC consumption is low at all

frequencies (~25 µA at 10 kSPS, ~240 µA at 1MSPS). An auto-shutdown function

guarantees that the ADC is powered off except during the active conversion phase.

The ADC can be served by the DMA controller. It can operate from a supply voltage down to

1.65 V.

The ADC features a hardware oversampler up to 256 samples, this improves the resolution

to 16 bits (see AN2668).

An analog watchdog feature allows very precise monitoring of the converted voltage of one,

some or all scanned channels. An interrupt is generated when the converted voltage is

outside the programmed thresholds.

The events generated by the general-purpose timers (TIMx) can be internally connected to

the ADC start triggers, to allow the application to synchronize A/D conversions and timers.

3.12

Temperature sensor

The temperature sensor (TSENSE) generates a voltage VSENSE that varies linearly with

temperature.

The temperature sensor is internally connected to the ADC_IN18 input channel which is

used to convert the sensor output voltage into a digital value.

The sensor provides good linearity but it has to be calibrated to obtain good overall

accuracy of the temperature measurement. As the offset of the temperature sensor varies

from chip to chip due to process variation, the uncalibrated internal temperature sensor is

suitable for applications that detect temperature changes only.

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